1. Field of the Invention
The present invention relates to semiconductor packages and fabrication methods thereof, and more particularly, to a stack-type semiconductor package having conductive posts and conductive balls for electrical connection and a fabrication method thereof.
2. Description of Related Art
In a stack-type semiconductor package, a plurality of solder balls are formed on upper and lower substrates and bonded together to electrically connect the upper and lower substrates. The height of the semiconductor package and the gap between the upper and lower substrates are controlled through the solder balls.
However, since the solder balls easily collapse during a reflow process, the height of the semiconductor package is difficult to control. Further, a large space is required at joints of the solder balls. Therefore, such a stack-type semiconductor package cannot meet the fine-pitch requirement.
FIGS. 1A and 1B are schematic cross-sectional views showing a semiconductor package 1 and a fabrication method thereof according to the prior art.
Referring to FIG. 1A, a first substrate 10 having a plurality of first bonding pads 101 is provided. A plurality of first solder balls 11 are formed on the first bonding pads 101 and a gap d1 is formed between the first solder balls 11. A semiconductor chip 12 is disposed on the first substrate 10 through a plurality of solder balls 121, and an encapsulant 13 is formed on the first substrate 10 to encapsulate the semiconductor chip 12 and the solder balls 121. The encapsulant 13 has a plurality of openings 131 exposing top and side portions of the first solder balls 11. Further, a second substrate 14 having a plurality of second bonding pads 141 is provided and a plurality of second solder balls 15 are formed on the second bonding pads 141 and corresponding to the first solder balls 11.
Referring to FIG. 1B, a reflow process is performed to bond the first solder balls 11 and the corresponding second solder balls 15 together, thereby forming a plurality of conductors 16.
However, since the first solder balls 11 and the second solder balls 15 easily collapse during the reflow process, the height of the semiconductor package 1 or the gap 17 between the encapsulant 13 and the second substrate 14 is difficult to control. Further, solder bridging easily occurs between the first solder balls 11 or the second solder balls 15 so as to cause a short circuit. In addition, a large space is required at the joints between the first solder balls 11 and the second solder balls 15. Therefore, the semiconductor package 1 cannot meet the fin-pitch requirement.
Therefore, there is a need to provide a semiconductor package and a fabrication method thereof so as to overcome the above-described drawbacks.